Understanding the structural basis of species selective, stereospecific inhibition for Cryptosporidium and human thymidylate synthase

FEBS Lett. 2019 Aug;593(15):2069-2078. doi: 10.1002/1873-3468.13474. Epub 2019 Jun 18.

Abstract

Thymidylate synthase (TS), found in all organisms, is an essential enzyme responsible for the de novo synthesis of deoxythymidine monophosphate. The TS active sites of the protozoal parasite Cryptosporidium hominis and human are relatively conserved. Evaluation of antifolate compound 1 and its R-enantiomer 2 against both enzymes reveals divergent inhibitor selectivity and enzyme stereospecificity. To establish how C. hominis and human TS (ChTS and hTS) selectively discriminate 1 and 2, respectively, we determined crystal structures of ChTS complexed with 2 and hTS complexed with 1 or 2. Coupled with the previously determined structure of ChTS complexed with 1, we discuss a possible mechanism for enzyme stereospecificity and inhibitor selectivity.

Keywords: Cryptosporidium hominis; X-ray crystallography; chiral recognition; enzyme stereospecificity; inhibitor selectivity; thymidylate synthase.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural

MeSH terms

  • Catalytic Domain
  • Cryptosporidium / enzymology*
  • Crystallography, X-Ray
  • Folic Acid Antagonists / chemistry
  • Folic Acid Antagonists / pharmacology*
  • Humans
  • Models, Molecular
  • Protozoan Proteins / antagonists & inhibitors
  • Protozoan Proteins / chemistry
  • Protozoan Proteins / metabolism
  • Species Specificity
  • Structure-Activity Relationship
  • Thymidylate Synthase / antagonists & inhibitors
  • Thymidylate Synthase / chemistry*
  • Thymidylate Synthase / metabolism*

Substances

  • Folic Acid Antagonists
  • Protozoan Proteins
  • Thymidylate Synthase